Works a treat, although I'm not getting nearly the framerate you guys are...

Even with render distance turned down to 2, and all the pretties off it still sits down at 10-15 fps.

Intend to look through the whole configs posted above in a bit - but quick question first...
Do you guys run it single player, or offload the server element to, well, a server. I have put a minecraft server docker container on one of my home machines, and it seems to work OK (Can play on it from another machine with decent framerate, so I don't think it should be a bottleneck..)

Did you get glxgears running at 60fps ? Do you have a heatsink installed ? I'm assuming your using a Pi3 with a 5.1V 2.5Amp power supply with good power cable ? Are you running Minecraft in a window or fullscreen ?

You can add a temperature monitor to the task bar incase your Pi is throttling down due to temperature.

I'm using a Pi3 with heatsink, open case, fan and sandisk extreme pro sd card and some overclocking.

Do you get different performance with either option?
I have a local server, dockerised on a reasonable PC - I get decent frame rates from my mac against it (but that's a gigabit network connection all the way)

Did you get glxgears running at 60fps ? Do you have a heatsink installed ? I'm assuming your using a Pi3 with a 5.1V 2.5Amp power supply with good power cable ? Are you running Minecraft in a window or fullscreen ?

glxgears ran at 60fps
No heatsink
Pi3 with a decent enough PSU affect (think it's 2A rated)
Minecraft in a window or fullscreen (faster in a window)

You can add a temperature monitor to the task bar incase your Pi is throttling down due to temperature.

I'm using a Pi3 with heatsink, open case, fan and sandisk extreme pro sd card and some overclocking.

I'll check temperature, but I wouldn't expect that to be an issue - I'll report back.
Pi3 in a case, no h/s or fan, new class 10 card for the installation.

I'll check temperature, but I wouldn't expect that to be an issue - I'll report back.
Pi3 in a case, no h/s or fan, new class 10 card for the installation.

Definitely get a heatsink. You'll want one as a bare minimum since these things run really hot under full load. The Pi3 starts throttling at 80 degrees Celsius, and I bet it's hitting that temp before Minecraft even loads the welcome screen while in a case with no heatsink.

Currently I struggle to get more than 6 FPS in game.
Highest I've hit is about 13 FPS.

glxgears hits in the high 70 FPS range, and CPU usage averaging at 72-76%.
I have Overclocked, CPU frequency is set to 1350 MHz, SDRam frequency at 500 MHz, GPU memory set to 192 MB, frequency at 500 MHz, and the core frequency at 500. I do have an over voltage of 4. I have a RPi 3B, and this is the same framerate I was getting at stock. Part of me believes that Berryboot is to blame, as everyone else here is seemingly getting 40 FPS+ no problem.

Unfortunately, with it enabled I have a few issues at boot, namely the fact that Berryboot does not play nicely with OpenGL.
It'll boot into Raspbian after a short time, which isn't the problem, I just need to disable it if I want to boot into something else, otherwise it works much, much better. Like, 30 FPS on average better. Thanks.

I've tried to get forge to play Tekkit Classic, Because the technic launcher doesn't work. I get forge, Try my best to edit the run.sh file, But after hours of editing and looking things up, I get stuck at this error.

Did you re-copy the class path as described in the very last section of the tutorial :

If you want to attempt getting a new version of Minecraft working :

1 Install required version using java -jar Minecraft.jar - and allow to crash
2 Scroll up in terminal window and find last ../jre/bin/java command, scroll across and find ‘-cp ’, copy this path list until ‘ net.minecraft.launchwrapper.Launch’
3 Paste this text into the cp= in the run.sh script

Did you re-copy the class path as described in the very last section of the tutorial :

If you want to attempt getting a new version of Minecraft working :

1 Install required version using java -jar Minecraft.jar - and allow to crash
2 Scroll up in terminal window and find last ../jre/bin/java command, scroll across and find ‘-cp ’, copy this path list until ‘ net.minecraft.launchwrapper.Launch’
3 Paste this text into the cp= in the run.sh script